The sector for the automatic sorting of objects such as luggage, packages, letters, flat items, envelopes, dispatch parcels and containers of a varying nature is conventionally divided into two main types of systems: “letter-type” systems, where unloading of the object is performed in a direction coinciding with the direction of advancement of the conveyor, and “cross-belt” systems, where unloading is performed transversely with respect to the direction of advancement.
The latter systems are arranged mainly in a horizontal plane, the advantage of having a flexible sorting apparatus being offset by the problems associated with the large dimensions of the system.
In order to overcome the aforementioned problems, sorting machines of the so-called “cross-belt” type provided with carriages which are self-propelled along a vertical closed-loop path have been developed. In this case also, the system suffers from a drawback associated with overturning of the carriages along the bottom section of the path, which substantially reduces the loading capacity of the system.
In fact, along the semi-circular sections which join together the straight sections of the path, the conveying units undergo a rotation, through 180°, of the surface on which the transported objects are loaded (FIG. 2 of patent publication U.S. Pat. No. 3,662,874 illustrates schematically the overturning movement). This drawback, as can be understood, has a significant adverse effect on the loading capacity of the sorting machine since only half of the overall travel of the conveying units is exploited from an operational point of view.